COMPLEX STUDIES OF MAGNETIC CP STARS. III.ANALYSIS OF VARIABILITY AND EVOLUTIONARY STATUS MAGNETIC CP - STARS θ AUR

Abstract

Based on complex observations, the characters of the photometric, magnetic and spectral variability, with a period of P = 3d.6188, of the magnetic CP of the star θ Aur = HD 40312 were studied. The phase curves of the magneticfield (Be), brightness (V ) and equivalent widths (Wλ) of the lines of peculiar elements (Si, Cr, Sr, etc.) are constructed, by means of which the phases corresponding to the maximal peculiar (P) and normal region (N) onthe surface of the star are determined. It is revealed that all phase dependences are synchronous; that is, the extrema of the values of Be,V, and Wλ coincide within the error (φ = ±0.05). Hydrogen line profiles (Hγ,Hδ) were used to determine the fundamental parameters (Te and log g) for the normal (Te = 8800 K, log g = 3.65) and peculiar (Te = 9800 K, log g = 3.90) regions on the stellar surface. The effective temperature was also determined from the photometric indices (Te = 10100 K and 9500 K ). The location of the star θ Aur on the Hertzsprung-Russell diagram has been established, and thus its evolutionary status has been determined. It was found  that the star HD 40312 is located closer to the upper boundary (TAMS) of the MS band.